148 lines
3.6 KiB
Diff
148 lines
3.6 KiB
Diff
From d58f078ce2d53e5dab6b3d0d5f960504268e1894 Mon Sep 17 00:00:00 2001
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From: Martin Liska <mliska@suse.cz>
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Date: Wed, 12 Aug 2020 09:21:51 +0200
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Subject: [PATCH] ipa: fix bit CPP when combined with IPA bit CP
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As mentioned in the PR, let's consider the following example:
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int
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__attribute__((noinline))
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foo(int arg)
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{
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if (arg == 3)
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return 1;
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if (arg == 4)
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return 123;
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__builtin_unreachable ();
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}
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during WPA we find all calls of the function
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(yes the call with value 5 is UBSAN):
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Node: foo/0:
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param [0]: 5 [loc_time: 4, loc_size: 2, prop_time: 0, prop_size: 0]
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3 [loc_time: 3, loc_size: 3, prop_time: 0, prop_size: 0]
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ctxs: VARIABLE
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Bits: value = 0x5, mask = 0x6
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in LTRANS we have the following VRP info:
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# RANGE [3, 3] NONZERO 3
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when we AND masks in get_default_value we end up with 6 & 3 = 2 (0x010).
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That means the only second (least significant bit) is unknown and
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value (5 = 0x101) & ~mask gives us either 7 (0x111) or 5 (0x101).
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That's why if (arg_2(D) == 3) gets optimized to false.
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gcc/ChangeLog:
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PR ipa/96482
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* ipa-cp.c (ipcp_bits_lattice::meet_with_1): Drop value bits
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for bits that are unknown.
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(ipcp_bits_lattice::set_to_constant): Likewise.
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* tree-ssa-ccp.c (get_default_value): Add sanity check that
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IPA CP bit info has all bits set to zero in bits that
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are unknown.
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gcc/testsuite/ChangeLog:
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PR ipa/96482
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* gcc.dg/ipa/pr96482.c: New test.
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---
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gcc/ipa-cp.c | 3 +-
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gcc/testsuite/gcc.dg/ipa/pr96482.c | 44 ++++++++++++++++++++++++++++++
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gcc/tree-ssa-ccp.c | 3 ++
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3 files changed, 49 insertions(+), 1 deletion(-)
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create mode 100644 gcc/testsuite/gcc.dg/ipa/pr96482.c
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diff --git a/gcc/ipa-cp.c b/gcc/ipa-cp.c
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index 945a69977f3..2b21280d919 100644
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--- a/gcc/ipa-cp.c
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+++ b/gcc/ipa-cp.c
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@@ -1011,7 +1011,7 @@ ipcp_bits_lattice::set_to_constant (widest_int value, widest_int mask)
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{
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gcc_assert (top_p ());
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m_lattice_val = IPA_BITS_CONSTANT;
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- m_value = value;
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+ m_value = wi::bit_and (wi::bit_not (mask), value);
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m_mask = mask;
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return true;
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}
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@@ -1048,6 +1048,7 @@ ipcp_bits_lattice::meet_with_1 (widest_int value, widest_int mask,
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widest_int old_mask = m_mask;
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m_mask = (m_mask | mask) | (m_value ^ value);
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+ m_value &= value;
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if (wi::sext (m_mask, precision) == -1)
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return set_to_bottom ();
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diff --git a/gcc/testsuite/gcc.dg/ipa/pr96482.c b/gcc/testsuite/gcc.dg/ipa/pr96482.c
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new file mode 100644
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index 00000000000..68ead798d28
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--- /dev/null
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+++ b/gcc/testsuite/gcc.dg/ipa/pr96482.c
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@@ -0,0 +1,44 @@
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+/* PR ipa/96482 */
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+/* { dg-do run } */
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+/* { dg-options "-O2 -flto" } */
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+/* { dg-require-effective-target lto } */
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+
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+int
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+__attribute__((noinline))
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+foo(int arg)
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+{
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+ if (arg == 3)
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+ return 1;
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+ if (arg == 4)
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+ return 123;
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+
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+ __builtin_unreachable ();
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+}
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+
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+int
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+__attribute__((noinline))
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+baz(int x)
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+{
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+ if (x != 0)
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+ return foo(3); /* called */
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+
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+ return 1;
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+}
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+
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+int
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+__attribute__((noinline))
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+bar(int x)
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+{
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+ if (x == 0)
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+ return foo(5); /* not executed */
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+
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+ return 1;
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+}
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+
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+int main(int argc, char **argv)
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+{
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+ if (bar(argc) != baz(argc))
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+ __builtin_abort ();
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+
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+ return 0;
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+}
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diff --git a/gcc/tree-ssa-ccp.c b/gcc/tree-ssa-ccp.c
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index 7e3921869b8..65dffe06530 100644
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--- a/gcc/tree-ssa-ccp.c
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+++ b/gcc/tree-ssa-ccp.c
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@@ -306,6 +306,9 @@ get_default_value (tree var)
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{
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val.lattice_val = CONSTANT;
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val.value = value;
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+ widest_int ipa_value = wi::to_widest (value);
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+ /* Unknown bits from IPA CP must be equal to zero. */
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+ gcc_assert (wi::bit_and (ipa_value, mask) == 0);
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val.mask = mask;
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if (nonzero_bits != -1)
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val.mask &= extend_mask (nonzero_bits,
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--
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2.28.0
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